1. Technical Field
This application relates to a drill for use in a machine tool with a major cutting edge divided into two partial cutting edges by a chisel edge (4), one partial cutting edge of which is a guide cutting edge (5) with a guide land (13) on its end farther from the chisel edge (4) in the radial direction (10), and with a support land (14) on the guide cutting edge/minor clearance face (11) associated with the guide cutting edge (5), such that the support land (14) and the guide land (13) between them form the boundaries of the guide cutting edge/minor clearance face (11) in the direction of rotation (3) of the drill.
2. Background Information
An example of a drill of this type is shown in EP-B-290 520 (Corresponding to U.S. Pat. No. 4,913,603), for example. This document also describes the problem known in the technical literature as “chatter”, a problem that is experienced with drill during the drilling process when the irregular rotational action of the drill during the drilling process results in an irregular surface structure of the boring wall. This phenomenon is due in particular to the fact that linear or spiral chip flutes are shaped into the generated surfaces of the drills to remove the chips that are formed during the drilling process. Frequently, the chip flutes on one hand and the cutting edges of the drill on the other hand are distributed symmetrically over the periphery of the drill. This symmetrical distribution has the further disadvantage that the vibrations of the drill that cause the “chatter” recur periodically during the drilling process. This periodic recurrence of the vibrations causes an increase in the amplitude of the vibrations, i.e. a “build-up” of the chatter during the drilling process, with the result that the irregularities in the side walls of the hole which is being bored, which irregularities are also called ““chatter marks”” increase, resulting in a deterioration in the quality of the boring over the length of the drilling process.
To reduce this technical problem, the above referenced publication, for example, indicates that the minor cutting edges of the drill that are present on the drill periphery can be provided with lands. These lands are generally snug up against the inside wall of the boring and act on the drill in the manner of support fins. The publication describes the placement of a plurality of lands on the different cutting edges of the drill. An additional measure to prevent the untrue running of the drill is the asymmetrical arrangement of the chip flutes and correspondingly of the drill cutting edges. This measure is also described in the above referenced EP-B-290 520 (Corresponding to U.S. Pat. No. 4,913,603).